Means for forming the teeth of spur gear wheels or the like



y 1959 w. H. BATEMAN 2,893,173

MEANS FOR FORMING THE TEETH OF SPUR GEAR-WHEELS OR THE LIKE Filed. May25,1955 v s Sheets-Sheet 1 i. I v I 32 8: 1 k is I Fife 1 1 I I 1 28 E1s 1 1 I] i 24 E z i R t l Fig.1

July 7, 1959 I w. H. BATEMAN 2,893,173

MEANS FOR FORMING THE TEETH OF SPUR GEAR WHEELS OR THE LIKE Filed May25, 1955 3 Sheets-Sheet 2 July: 7, .1959 w. H. BATEMAN 2,893,173

- MEANS FOR FORMING THE TEETH OF SPUR GEAR WHEELS OR THE LIKE Filed May23, 1955 5 Sheets-Sheet 3 United States Patent MEANS FOR FORMING THETEETH 0F SPUR GEAR WHEELS OR THE LIKE William Henry Bateman, Overstream,Loudwater, Rickmansworth, England, assignor to Wickman Limited,Coventry, England Application May 23, 1955, Serial No. 510,314

Claims priority, application Great Britain May 24, 1954 4 Claims. (CI.51-95) This invention relates to the forming of the teeth of spur gearwheels, shaft splines, or like parts of analogous work pieces, by meansof the kind wherein the forming is effected by a rotary grinding orcutting tool having a helically shaped periphery, and wherein theworkpiece is rotated during the forming operation at a rate such aswould result by meshing the workpiece with a worm of the same pitch asthe tool.

A disadvantage of the means hitherto employed for the purposes abovementioned has been the need for providing complex mechanism for enablingthe wear of the tool to be uniformly distributed over the axial lengthof the tool, thereby obviating localisation of the wear.

The object of the present invention is to enable the desireddistribution of wear of the tool to be effected in a simplified manner.

The invention consists of a means of the aforesaid kind, wherein therelative feed movement of the workpiece and tool is effected in adirection which is inclined to the rotation axis of the workpiece, andwherein the rotation axis of the tool is inclined to the direction ofthe feed movement and sensibly at a right angle to the rotation axis ofthe workpiece.

The invention also comprises a means as defined in the precedingparagraph wherein the means for imparting rotational movement to theworkpiece include a pair of interengaging gear members one of which isslidable relatively to the other.

Moreover the invention comprises a machine substantially as hereinafterdescribed for effecting the operations above defined.

In the accompanying drawings, Figure 1 is a sectional front elevation,Figure 2 a sectional side elevation, and Figure 3 a plan illustrating amachine in accordance with the invention in this example for grindingthe teeth of a plain spur wheel.

Referring to the drawings, there is provided on a base 1, a guide 2 forcarrying a horizontally movable slide 3, the latter being movable alongthe guide by any convient mechanism such as a hydraulic cylinder 40provided with a reciprocal piston 41 connected to the slide 3 by the rod42 and operated by reversing pump 43, which may be controlled manuallyor otherwise according to the requirements. On the bed is formed orsecured a bracket 4 on which is provided a vertical guide 5, and on thisguide is carried a slide 6 on which is mounted an electric motor 7 forrotating the helical grinding wheel 8, which latter is secured to oneend of the rotary spindle 9 of the motor. Any convenient means (notshown) is combined with the guide for raising and lowering the slide 6.

On the slide 3 is mounted a spindle 10 to which is secured the workpiece11, the spindle 10 being supported at one end by a bearing 12 and at theother end by a tail stock 13. The spindle 10 is connectible by a clutch14 to a spindle 15 which preferably is embraced by a friction brake 16for damping transient fluctuations in 2,893,173 Patented July 7, 1959ice the movements of the spindle, and this spindle is connected by atrain of change-speed gear wheels 17 to another spindle 18.

'In the particular arrangement shown, the spindle 9 of the motor isdisposed at an angle of relatively to the longitudinal centre line ofthe slide 2, the axis of the work-carrying spindle It) being arranged ata nominal right angle to the axis of the spindle 9.

The spindle 15 is coaxial with the spindle 10, and the spindle 18 isparallel with the spindle 15.

In the bed of the machine is mounted a long helically toothed wheel 19carried by a spindle 20. Its axis is parallel with the longitudinalcentre line of the guide 2, and in this example, its teeth are inclinedat 10 to its axis. Engaging with this pinion is a corresponding helicalpinion 21 carried by a spindle 22 on the slide 3, the spindle 22 beingconnected to the above mentioned spindle 18 through a pair of bevelpinions 23.

The helically toothed wheel 19 is driven by an electric motor 24 throughworm reduction gearing 25 and a change-speed train of gear wheels 26.Preferably a flywheel 27 is combined with the said worm gearing tominimise transient fluctuations of motion.

The two motors 7 and 24 are synchronous alternating current motors, andto prevent relative movements of their rotors the latter areinterconnected by coaxial spindles 28, 29, a clutch 30 and bevel pinions31, 32.

In brief, the mode of action of the machine is such that by linearmovement of the slide 3 the whole length of the workpiece is subjectedto the action of the grinding wheel, and by reason of the inclination ofthe axis of the workpiece relatively to the direction of motion of theslide the workpiece has a component of motion parallel with the axis ofthe grinding wheel, the amount of this component being such as willcause the workpiece to move across the whole of the axial length of thegrinding wheel, thereby ensuring uniform wear of the whole length of thehelix of the grinding wheel.

The kinematics involved in the actions of the machine will now beexplained more fully. Let it be supposed that the grinding wheel isreplaced by an identically similar worm, and that a finished workpieceis mounted in position, but free from engagement with any of theassociated gearing above described, the slide 3 being stationary. Itwill be obvious that on rotating the worm a corresponding rotation willbe imparted to the workpiece. Now let it be supposed that the worm isheld stationary, and that a linear movement is imparted to theworkpiece. It will be equally obvious that this will result in arotational movement of the workpiece, this movement being termed thecompensatory rotation. From this it follows that when the worm isrotated, and the workpiece is simultaneously given a linear movementrelatively to the Worm, the workpiece will have imparted to it not onlythe above mentioned rotational movement but also the additionalcompensatory rotational movement.

For the purpose of the invention it is required that during linearmovements of the slide 3, the workpiece shall have imparted to it notonly a normal rotational movement such as would be imparted to it (whenstationary) by a worm corresponding to the grinding wheel, but also theabove mentioned compensatory rotational movement, and this latterrequirement is satisfied by the inclination of the teeth of the helicalwheel 19.

It will be understood, however, that the angle between the two spindles9 and 10 will depend to some extent on the helix angle of the grindingwheel. With a grinding wheel initially of about 12' diameter and havinga helix angle of about 1.5 degrees, the said angle between the spindles9 and 10 could be precisely and the small lack of parallelism betweenthe helix of the grinding wheel and the teeth of the workpiece would beof no practical consequence. But with reduction of diameter of thegrinding wheel resulting from wear and repeated trimmings to, say, theconsequent increase of the helix angle may necessitate the adoption of acompromise angle between the spindles 9 and 10 which could bring thehelix of the grinding wheel into sufliciently close parallelism withteeth of the workpiece throughout the normal life of the grinding wheel.It follows that the angle between the spindles 9 and 10 may differ by afew degrees from 90 to accommodate the obliquity of the helix of thegrinding wheel.

Thus the inclination of the workpiece axis to the direction of feed isinvariable, i.e., is substantially at right angles and is referred toherein, and in the claims, as at a fixed angle, which may be onlymodified slightly (as explained'in the previous paragraph) toaccommodate the lead of the helix of the grinding wheel periphery.

A further requirement to be satisfied is that the same machine shall becapable of dealing with workpieces of different diameters. It will beevident that the rate of rotation that can be imparted to :a workpieceby a given worm depends on the diameter of the workpiece. It will bealso evident that the compensatory movement to be imparted to allworkpieces must be in inverse proportion to their diameters whenexpressed in degrees of rotation, and uniformly in terms of length alongtheir circumferences. Consequently it is necessary to make provisionwhereby the rate of rotation of the workpiece to be treated'by thegrinding wheel can be varied in a manner appropriate to the diameter ofthe workpiece. This requirement is met by combining with the Wheels 19,21, a changeable wheel train 26 for driving the wheel 19, and anotherchangeable wheel train 17, for transmitting motion from the wheel 19 tothe spindle 10.

Moreover, the invention is not limited to a means for treating gearwheels, as it may be applied also to forming shaft splines, orperforming other analogous grinding or cutting operations by means of ahelical grinding wheel or cutting tool.

In the illustrated example, the grinding wheel 8 is considered as beingof such diameter and the thread thereof of such pitch that the leadangle of the thread is so slight as to admit of the axis of thework-carrying spindle 10 being at substantially a right angle to theaxis of the spindle 9. This angle, however, is referred to herein and inthe claims as being nominal, inasmuch as this may vary through anangular range, say, of

substantially 80 to 100 to accommodate various pitch angles of thegrinding wheel thread (in a right or in a left hand direction) such asmight occur where a grinding wheel of smaller diameter is used withcorrespondingly greater pitch angle for any given pitch.

It will be apparent, of course, that such variation of the nominal rightangle between the axes of the spindle 10 on the spindle 9 would beaccompanied by the appropriate ratio of compensatory gearinghereinbefore referred to, to properly meet the requirements of theangular relationship between the work-carrying spindle 10 and thespindle 9.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. In a machine for grinding the teeth of spur gear wheels, splines andsimilar non-helical workpieces in which the teeth lie in the directionof their lengths parallel with the axis of the workpiece by a grindingwheel having an operative peripheral surface of helical form, thecombination of a grinding wheel spindle, a work spindle, a work spindlesupporting table, means for irnparting linear movement to said table ina direction inclined to the axis of the work spindle and at a fixedangle to the axis of the grinding wheel spindle whereby planescontaining the axes of both spindles together with the direction ofmovement of the table form a triangle, interengaging gear members forinter-connectingly transmitting rotation from a driving source to thegrinding wheel spindle and the work spindle including a gear slidablewith the said table parallel with the axis of another gear in meshingengagement, thereby providing relative rates of rotation of the grindingwheel spindle and the work spindle corresponding to rates which wouldresult if a workpiece derived its rotation from the grinding wheelthroughout movements of the said table.

2. A machine as claimed in claim 1, which includes a changeable train ofgear wheels for imparting motion from a source to one of the pair ofinterengaging gear members, and which includes another changeable trainof gear wheels for transmitting motion from the other of theinterengaging gear members to the workpiece.

3. A machine as in claim 1, wherein one of the interengaging gearmembers is mounted for rotation only and is of increased length relativeto the slidable interengaging gear member.

4. In a machine for forming the teeth of spur gears, splines and similarworkpieces wherein the teeth lie in a direction parallel with the axisof the workpiece, a grinding wheel having an operative peripheralsurface of a helical form, a work spindle, a grinding wheel spindle, awork spindle supporting table, a work table slide movably relatively tothe grinding wheel along a line which is inclined at a fixed anglerelatively to the rotation axis of the grinding wheel, and gearingconnecting the grinding wheel and work spindles, said gearing includinga pair of relatively slidable and inter-engaging helical wheels, thesliding movement of one of which wheels is effected by the work-tableslide, and change speed gear wheels for varying the rate of rotation ofthe workpiece spindle.

References Cited in the file of this patent UNITED STATES PATENTS2,424,191 Rickenmann July 15, 1947 2,449,354 Wickman Sept. 14, 19482,528,242 Praeg Oct. 31, 1950 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION- Patent No. 2,893.11?) July 7 1959 William Henry Bateman Itis hereby certified that error appears in the printed specification ofthe above numbered patent requiring correction and that the said LettersPatent should read as corrected below.

Column 2 line 69 for "12" read 12" --g column 3, line 13, for"workpiece" read grinding wheel Signed and sealed this 4th day ofOctober 1960.

(SEAL) Attest:

KARL H. AXLI NE Attesting O flicer ROBERT C. WATSON Commissioner ofPatents

